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Three Phase Electro-catalysis: A Step Forward for Polymer-grade Ethylene Purification

Update time:2021-07-13

Chinese scientists have recently achieved high performance electrochemical acetylene reduction at room temperature. This has shown special advantages compared to conventional thermal hydrogenation strategy which has been applied for over fifty years. 


The study, published online in Nature Catalysis, was directed by Prof. ZHANG Tierui from the Technical Institute of Physics and Chemistry (TIPC) of the Chinese Academy of Sciences, and Prof. WANG Haotian from Rice University.  


Ethylene industry is crucial to a country's petrochemistry. Industrial ethylene is coming from the cracking of hydrocarbons, such as naphtha. Cracking products contain 0.5-2.0% acetylene impurities inevitably. The impurities will poison Ziegler Natta catalyst used for ethylene polymerization and affect the quality of polymer products. Therefore, it is necessary to reduce the concentration of acetylene impurities to parts per million (ppm) before polymerization.  


“We usually use the acetylene thermal hydrogenation currently. However, the required operational temperature is higher than 100℃ and excessive hydrogen is required. Ethylene will therefore over-hydrogenated to ethane,” said Dr. SHI Run from TIPC, one of the co-first authors. 


“The purpose of our research is to develop a ‘gas-solid-liquid’ three phase electro-catalytic acetylene reduction (EAR) system. Therefore, nanomaterial such as Cu/Cu2O derived from layered double hydroxides could be used as catalyst to realize the selective reduction of acetylene in ethylene rich feed gas at room temperature,” Dr. SHI introduced. 


In the work, the conversion rate of acetylene reached 99.9%. Over 90% of ethylene selectivity was achieved. Acetylene concentration was successfully reduced from 5000 ppm to less than 1 ppm. Core indexes (acetylene conversion, ethylene selectivity, hydrogen volume, reaction temperature and specific rate) of the EAR system outperform most of thermal hydrogenation investigations. 


Besides, the three phase electro-catalytic system only needs an electricity cost equals to 0.5% of the market price of ethylene. It is therefore highly possible to become an alternative solution to replace existing acetylene conversion technologies for the production of polymer-grade ethylene. 


This work was supported by the National Key Projects for Fundamental Research and Development of China, the National Natural Science Foundation of China, and the International Partnership Program of the Chinese Academy of Sciences.

Figure. Schematic Diagram (Image by ZHANG group)